樊康祺

Harvesting energy from ambient mechanical vibrations by the piezoelectric effect has been proposed for powering microelectromechanical systems and replacing batteries that have a finite life span. A conventional piezoelectric energy harvester (PEH) is usually designed as a linear resonator, and suffers from a narrow operating bandwidth. To achieve broadband energy harvesting, in this paper we introduce a concept and describe the realization of a novel nonlinear PEH. The proposed PEH consists of a primary piezoelectric cantilever beam coupled to an auxiliary piezoelectric cantilever beam through two movable magnets. For predicting the nonlinear response from the proposed PEH, lumped parameter models are established for the two beams. Both simulation and experiment reveal that for the primary beam, the introduction of magnetic coupling can expand the operating bandwidth as well as improve the output voltage. For the auxiliary beam, the magnitude of the output voltage is slightly reduced, but additional output is observed at off-resonance frequencies. Therefore, broadband energy harvesting can be obtained from both the primary beam and the auxiliary beam.
School of Electronical & Mechanical Engineering, Xidian University, Xi’an 710071, China (Received 1 November 2013; revised manuscript received 23 December 2013; published online 10 June 2014)
Keywords: piezoelectric conversion, mechanical vibration, magnetic coupling, energy harvesting PACS: 45.20.dg, 46.70.De, 68.35.Gy DOI: 10.1088/1674-1056/23/8/084501 of a conventional linear PEH will decrease dramatically. In order to widen the operating bandwidth, and thus improve the performance of a PEH, several strategies have been proposed in recent years. The first strategy is to tune the resonant frequency of a PEH by applying mechanical preload, [16] using magnetic forces, [22] or piezoelectric actuators. [23] However, the complexity and power consumption of automatic tuning schemes may completely offset any improvement achieved in the performance of a PEH. [24,25] Multimodal energy harvesting is another strategy widely pursued for broadband purposes. This strategy can be utilized by integrating a piezoelectric cantilever array in one harvester, [26] or by exploiting two DOF PEH configurations. [27,28] In general, the purpose of developing a multimodal PEH is to achieve close resonances, but most of the multimodal energy harvesting schemes can only provide a discrete effective bandwidth. [28] In addition, multimodal energy harvesting increases the volume, and then reduces the energy density of a PEH. In very recent years, magnetic interaction has been frequently reported for broadband energy harvesting. Cotton et al. [9] developed a piezoelectric inverted pendulum with bistable state to enhance energy harvesting from stochastic vibrations. Lin et al. [24] and Ferrari et al. [29] proposed simplified models to study the effect of nonlinear magnetic force on the performance of a PEH. They found that the off-resonance response of a PEH can be substantially improved by magnetic coupling. The dynamic responses of nonlinear PEHs
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Chin. Phys. B Vol. 23, No. 8 (2014) 084501
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Broadband energy harvesting via magnetic coupling between two movable magnets
This content has been downloaded from IOPscience. Please scroll down to see the full text. 2014 Chinese Phys. B 23 084501 (/1674-1056/23/8/084501) View the table of contents for this issue, or go to the journal homepage for more
Broadband energy harvesting via magnetic coupling between two movable magnets∗
Fan Kang-Qi(樊康旗)† , Xu Chun-Hui(徐春辉), Wang Wei-Dong(王卫东), and Fang Yang(方 阳)
1. Introduction
Microelectromechanical systems (MEMS) and the relevant physical mechanisms have attracted significant attention over the past few years due to their potential applications in many industries. [1–7] Currently, these systems are being powered and sustained by batteries that fail to keep pace with the demands of such systems, especially in terms of energy density. [8] Moreover, batteries require frequent replacement/recharge, which is prohibitively expensive and cumbersome for a large quantity or in a remote area. Harvesting energy from ambient mechanical vibrations has been considered as a promising solution to this issue. [9–13] The ultimate aim is to implement self-powered systems. [11] Mechanical vibration can be converted into electrical energy as a power supply via electrostatic, [14] electromagnetic, [15] or piezoelectric transductions. [16–18] The piezoelectric transduction outperforms the others because of its high energy density, appropriate voltage and current outputs, strong electromechanical coupling, simple structure, and good compatibility with MEMS. [19–21] A conventional piezoelectric energy harvester (PEH) is generally designed as a single degree-offreedom (DOF) linear resonator. In order to harvest energy efficiently, the resonant frequency of the PEH must match the frequency of the vibration source. However, this requirement cannot always be guaranteed since the frequencies of the naturally occurring vibration sources usually vary in a certain range. With a slight drift from the resonance, the efficiency